基于光强轮廓结构的偏振无关高衍射效率二维光栅(特邀)

Polarization-Independent Two-Dimensional Grating with High Diffraction Efficiency Based on Light Intensity Profile Structure(Invited)

针对目前二维光栅设计结构单一、与实际结构不匹配的问题,提出一种金属-介质二维光栅。该光栅不仅具有优异的偏振无关性和高衍射效率,而且其结构更符合实际制备的形貌。基于双光束正交曝光单周期干涉场强度分布,构建基于光强轮廓的二维光栅设计结构,采用傅里叶模态法和粒子群算法对光栅进行优化设计。结果表明,最优参数下,设计的二维光栅在波长为780 nm处以Littrow角入射时,横电、横磁偏振光的衍射效率均大于95%,并且具有优异的偏振无关性和较大的制备容差。此外,对比同结构参数下传统圆台、棱台结构的二维光栅衍射效率,结果表明光栅结构的微小变化对二维光栅衍射效率的影响较大,基于光强轮廓的设计结构可有效提高光栅设计与实际的匹配度。研究工作可为位移测量领域高精度二维光栅的研制提供理论基础。

To solve the problem wherein the structure of a two-dimensional(2D)grating is single and does not match the actual structure,a 2D metal-medium grating is proposed that has excellent polarization independence and high diffraction efficiency and wherein the grating structure is more consistent with the actual topography.Based on the intensity distribution of a two-beam orthogonal exposure single-period interference field,a 2D grating structure based on a light intensity profile is constructed,and the grating is optimized using a Fourier mode method and particle swarm optimization algorithm.Results show that,under optimal parameters,the transverse electric and transverse magnetic polarized light diffraction efficiencies are greater than 95%when the designed 2D grating is incident at the Littrow angle at a 780-nm wavelength,and it exhibits excellent polarization independence and large preparation tolerance.In addition,a comparison of the diffraction efficiencies of traditional round and prism gratings with the same structural parameters reveal that a small change in the grating structure significantly affects the diffraction efficiency of the 2D grating.Finally,the designed structure based on a light intensity profile can effectively improve the matching degree between the design and actual grating.This research provides a theoretical basis for the development of high precision 2D grating in the displacement measurement field.